1. Field of the Invention
This invention relates to improvements in electromagnetic control fuel injection valves for internal combustion engines, particularly diesel engines, in which the injector needle or injection nozzle is opened by the pressure drop in a control chamber by means of a discharge conduit and closed by repressurizing the chamber. The discharging and charging of the fluid in the chamber is performed with a three-way solenoid valve.
2. Description of the Prior Art
Fuel injection valves are ordinarily be called "constant pressure injector" valves when the pressure that constantly prevails upstream from the seat of the injection needle of the valve allows the needle to rise when the control chamber, located above said needle, is discharged. Numerous examples of such injection systems are known but they are subject to two main criticisms.
First, these injection systems used on direct injection engines often give rise to a very noisy combustion. The gradient of instantaneous delivery or rate of introduction is very high from the start of injection since the constant high pressure is immediately present upstream from the fuel injection ports, which results in the introduction of a large quantity of fuel in the combustion chamber before start of ignition; the fuel in the cylinder at the moment of ignition being present in a greater quantity than in a conventional injection system, the gradient of the cylinder pressure is very high at the start of combustion, which results in noisy combustion.
Further, the control of a three-way solenoid valve is generally such that opening of the injector needle is often dependent upon the movement of the solenoid valve, which causes difficulties in the ability to control a stable, repetitive dosing of very small injected quantities.